Don't explicitly tear down code range in cctest/test-alloc/CodeRange to avoid double-free.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index a51cce42c2afdd5b0b217e22c350fe80a4aff278..4b2c40313ddd642425a32b571da0d8afb54f24ad 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -931,10 +931,6 @@ class CodeRange {
   // Returns false on failure.
   bool SetUp(size_t requested_size);
 
-  // Frees the range of virtual memory, and frees the data structures used to
-  // manage it.
-  void TearDown();
-
   bool valid() { return code_range_ != NULL; }
   Address start() {
     DCHECK(valid());
@@ -964,6 +960,10 @@ class CodeRange {
   void ReleaseEmergencyBlock();
 
  private:
+  // Frees the range of virtual memory, and frees the data structures used to
+  // manage it.
+  void TearDown();
+
   Isolate* isolate_;
 
   // The reserved range of virtual memory that all code objects are put in.